In general, when a mobile terminal performs an initial access in an orthogonal frequency division multiplexing access (OFDMA) system, the base station does not allow a predetermined mobile terminal to perform the initial access to the base station in a predetermined process, but a plurality of mobile terminals compete with each other to perform the initial access to the base station. In this case, when two or more mobile terminals perform the initial access to the base station at the same time, all the mobile terminals fail to perform the initial access.
To solve the above problem, a method for allocating more resources to the contention period has been suggested. However, since the resources allocated to the contention period are allocated to transmit user data, the resources are greatly consumed when the user data are transmitted.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.